1. Technical Field
This invention relates to a method of applying adhesive to a fiber optic canister. More particularly, a fiber optic canister is formed having at least two open channels. Adhesive is injected into at least one channel to impregnate the canister with adhesive.
2. Discussion
Wound optical fibers and wound wire coils are commonly used in military and communication applications. Typically, optical fibers are densely wound, layer by layer onto bobbins, to form extremely long wound filament items referred to as fiber optic coils, canisters, packs, etc. These items are often designed and wound to be useful in high speed payout applications.
It is known that high density deep nested filament winding techniques give rise to the formation of crossover regions in each filament layer. These regions are continuous from layer to layer and form natural open channels from the first layer through the last layer in a wound canister.
Many techniques used to form high density canisters require that an adhesive be used to enhance shelf life and to ensure that the filament peels off with proper control during payout. Unfortunately, the application of adhesive during winding is attended by several problems. For example, in one commonly used technique, adhesive is applied after each filament layer is wound. However, layer to layer application of adhesive requires that the winding process stop temporarily and thus prevents high speed production of canisters. In addition, adhesive tends to accumulate in the crossover regions (channels) which can cause problems during payout. Moreover, adhesive is often applied by spraying, which is very messy and can require the use of special shields to prevent inadvertent spraying of adhesive onto equipment, etc.
Another method of applying adhesive involves vacuum impregnation of a dry wound canister with adhesive. With this method, the canister is first dry wound without any adhesive, and then adhesive is injected into the entire item using a vacuum. This technique requires the use of a volatile solvent to reduce the viscosity of the adhesive so that the adhesive will flow in the vacuum. Unfortunately, many solvents actually boil off in such vacuums, resulting in the application of too much adhesive to the winding. One way around the problem of applying too much adhesive is to use a weak adhesive; however a weak adhesive is unacceptable in many military applications. In addition, a vacuum is ineffective in removing any excess adhesive which may have accumulated in the canister.
The use of an in line pressureless die to apply adhesives during winding of canister is also known. However, this approach requires expensive equipment and careful control to maintain adhesive uniformity. Moreover, reversal of the in line die process to correct for errors during winding is extremely difficult.